The invention relates to a method for operating an internal combustion engine, in particular a gasoline engine, of a motor vehicle, comprising a mixture pilot control by which at least one composition of an air-fuel mixture required for a predetermined target air-fuel mixture ratio is determined.
It is principally already known to make a correction or adaption of the metering of the fuel mass and/or the air mass to be fed to the combustion chamber as part of a pilot control of the fuel mass and/or the air mass in order to be able to more precisely set a target air-fuel ratio. Such a mixture adaption or the determination of the corresponding correction factors in today's vehicles is carried out in dependence of load, rotational speed and engine temperature.
A method for determining operating-point-dependent correction values for the composition of the air-fuel ratio is already known from DE 103 38 058 A1. In an operating phase of the internal combustion engine, correction values for different temperatures of the internal combustion engine are determined and stored upon reaching a first temperature threshold until reaching a predetermined operating temperature of the internal combustion engine, said correction values serving for the mixture pilot control and/or for the adaption. The correction values determined in this way are additionally linked with individual operating conditions or operating ranges of the engine so that correction values associated with the current operating point can be used for the mixture pilot control.
It is an object of the invention to provide a method that is improved with respect to the accuracy of the mixture adaption and the mixture pilot control. The method according to the invention and its advantageous configurations can be implemented by an implemented algorithm or a corresponding assembly arrangement in at least one control device provided for this purpose, in particular in an engine control device.
The underlying basis of the invention is a known method for operating an internal combustion engine, in particular a gasoline engine, of a motor vehicle, comprising a mixture pilot control and a lambda control, wherein at least one composition of an air-fuel mixture required for a predetermined target air-fuel ratio is determined by the mixture pilot control, and operating-parameter-dependent correction factors for the composition of the air-fuel mixture determined by the mixture pilot control are determined from the deviation of the current actual air-fuel ratio from the predetermined target air-fuel ratio (corresponding to step 102 of FIG. 1). The determined correction factors are then taken into account for the composition of the air-fuel mixture to be determined by the mixture pilot control.
According to the prior art, only correction factors that depend on load and/or rotational speed and/or engine temperature are determined heretofore, i.e., when determining the composition of the air-fuel mixture, a correction factor determined for these operating parameter values is taken into account depending on the current load, the rotational speed and the engine temperature.
The invention is based on the knowledge that the at present conventional correction of the mixture pilot control by the operating-parameter-dependent correction factors, which depend only on the load, the rotational speed and the engine temperature, are too inaccurate so that with the mixture pilot control alone, the predetermined air-fuel ratio can be adjusted only very roughly in operating situations in which the lambda control is not ready for use (yet). From the time, the lambda control is actually ready for use, a significant (re)adjustment of the lambda value (air-fuel ratio) is therefore still necessary.